Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h,w=map(int,input().split())
G=[]
white=0
for _ in range(h):
    s=input()
    white+=s.count('.')
    G.append(s)

vis=[[0]*w for _ in range(h)]
vis[0][0]=1

from collections import  deque
que=deque([(0,0,1)])

move=[(1,0),(-1,0),(0,1),(0,-1)]

while len(que)>0:
    ni,nj,c=que.popleft()
    for di,dj in move:
        mi,mj=ni+di,nj+dj
        if 0<=mi<h and 0<=mj<w and G[mi][mj]=='.' and vis[mi][mj]==0:
            vis[mi][mj]=c+1
            que.append((mi,mj,c+1))

print(white-vis[-1][-1]) if vis[-1][-1]!=0 else print(-1)